Swing-and-hit device for ball games

ABSTRACT

A swing-and-hit device for ball games includes a handle portion, a barrel portion having a predetermined length for swinging and hitting a ball or the like, and a substance having a property of dynamic moment of inertia being disposed in the swing-and-hit device close to the handle portion. The substance is located close to the handle portion when the swing-and-hit device is normally raised before being swung to hit a ball or the like, and moves toward an impact spot on the barrel portion due to the dynamic moment of inertia when the device is swung to hit the ball or the like. The swing-and-hit device for ball games loaded with the substance having the property of dynamic moment of inertia enables faster swing velocity, reduced muscle-exerted strength, increased effective impact energy, and better cushion effect to avoid possible sport-caused injury due to vibration of the swing-and-hit device after impact.

FIELD OF THE INVENTION

[0001] The present invention relates to a swing-and-hit device for ball games, and more particularly to sports goods, such as baseball bats, golf clubs, tennis and badminton rackets, etc., that are made of metal or composite material and have dynamic moment of inertia to enable faster swing velocity, reduced muscle-exerted strength, increased effective impact energy, and better cushion effect to avoid injury of user due to impact-caused vibration of such sports goods.

BACKGROUND OF THE INVENTION

[0002] In view of various kinds of increasingly fierce athletic sports, people require more sports goods that have upgraded quality and improved performance to provide sufficient comfortableness and protectiveness, to avoid sport-caused injuries, and to enable better athlete performance. For sports that involve the use of different sports goods, the design of the sports goods is a key having important influence on the athlete's performance. Baseball is a typical example of many sports to be played with specific sports goods.

[0003] And, a bat is the most important attacking means in playing baseball.

[0004] Baseball is an all-round sport combining the skills of pitching ball, running base, batting, and catching and passing ball. Baseball is also a sport including two important elements, that is, attack and defense. Attack and defense are two necessary sides of baseball game. A powerful attack is the best defense, and a perfect defense is the best attack. In playing baseball, batting is an active attacking weapon and also a very difficult sportive skill. In brief, good batting is a major condition to win in a baseball game. Generally speaking, a batter's swing velocity is an important factor that decides the batting power. It is known the process of batting includes two stage's, namely, the stage of visually judging the course of ball, and the stage of swing bat. When a batter swings the bat faster, he would have a relatively longer time to observe the location, the trajectory, and the speed of the moving ball, and could therefore more accurately judge the direction and course of the ball, and accordingly, has higher percentage of effective hitting of the ball. Moreover, according to the theorem of conservation of momentum and the impact principle, the faster the batter's swing velocity is, the higher the flying speed of the impacted ball is, and the longer the flying distance of the impacted ball is.

[0005] Therefore, it is an important way to upgrade the baseball player's swing velocity by improving the batter's batting power. Past studies indicated that swing velocity could be significantly improved through swinging bats of different weights, including weighting bat, light bat, and normal bat, over a long period of time (Sergo & Boatwright, 1993; DeRenne et al, 1995). However, in the swing warm-up before the game, most baseball players prefer to use the weighting bat that does not actually improve the swing velocity (DeRenne et al, 1992). In the study conducted by Otsuji et al in 2002, it is found swinging the weighting bat in the swing warm-up has only a psychological effect without any other biodynamic advantage. As a matter of fact, the batter's quality, the characteristics of ball, and the characteristics of bat all are factors having influence on effective batting. The batter's quality can be further divided into many important elements, including the batter's physical conditions, such as explosive strength, muscular strength, coordinating ability, etc., the batter's mental conditions, such as pressure-resistant ability, visual perception, etc., and the batter's professional skills, such as the ability of energy transfer, the bat-swinging course and trajectory, the hitting spot, etc. The characteristics of ball include the coefficient of restitution (COR) of the ball, the pitcher's pitching velocity, the hitting spot on the ball, etc. And, the characteristics of bat include the flexural properties, the trampoline effect, and the curvature of the bat (Hendee et al, 1998), the coefficient of restitution of the bat (Adair, 1990), the material of the bat, such as aluminum, titanium, carbon fiber, and other composite materials (Vizard, 1992), the configuration of the bat, the position of sweet spot on the bat (Brody, 1986), and the moment of inertia of the bat (Shiang et al, 1998).

[0006] As shown in Table 1, the characteristics of the baseball bat may be functionally divided into two major categories, namely, characteristics enabling improved batting performance, and characteristics enabling better comfortableness of using the bat to reduce sport-caused injuries.

[0007] By “enabling improved batting performance”, it means the bat has an enhanced power. A simple definition for the bat power is the power of the bat to transfer its energy to a ball when the bat impacts the ball. A ball speed produced after impacting on the ball with the bat may be a basis for judging the bat power. The bat power is particularly important in nowadays baseball games that stress powerful attacking.

[0008] To reduce injuries is to improve the comfortableness during batting. By “comfortableness”, it means a feeling of the batter at the instant of hitting and transferring impact energy from the bat to the batter's body. A minor discomfort would affect the batter's feeling of hitting, and a serious discomfort might result in sport-caused injuries. There are two major factors that result in uncomfortable feeling at batting, namely, the sting caused by the impact or shock at the instant of hitting the ball, and the vibration of bat due to impacting the ball with the bat.

[0009] All the currently available bats are designed to meet only one of the above two requirements. That is, there is not any baseball bat available in the markets capable of enabling improved player performance and reduced sport-caused injuries at the same time. TABLE 1 Characteristics of Bat

[0010] Both the above two functions of the bat have connection with the so-called Sweet Spot. The sweet spot refers to an area on a bat containing locations best for hitting a ball (Brody, 1986). Generally speaking, there are three different definitions for the sweet spot as follows:

[0011] 1. A power center, that is, a location at where the bat hits the ball to produce a maximum ball speed.

[0012] 2. A center of percussion, that is, a location at where the bat hits the ball without causing an impact feeling at a handle portion of the bat.

[0013] 3. A node, that is, a location at where the bat hits the ball without causing a vibration feeling at the handle portion of the bat.

[0014] In fact, the best hitting point is not located at the outmost distal end of the bat but at a point away from the distal end by a certain suitable distance. This point is also the location for the center of percussion and the node, and is the location for the so-called sweet spot. Thus, the sweet spot actually refers to an area on the bat covering the power point, the center of percussion, and the node.

[0015] The moment properties of bat include the mass, the center of mass, and the moment of inertia of the bat. The higher the mass of the bat is, the larger the impact energy generated by the bat is. However, a high mass would adversely affect the swing velocity. Reversely, a bat having lower mass could be more easily swung and controlled. That is, the batter would have sufficient time to get ready for swinging the bat but could create only limited impact energy. The location of the center of mass varies with different mass and shape of the bat. It is preferable the center of mass of the bat is located as close to the distal end of the bat as possible. By “moment of inertia”, it means a physical energy that affects the degree of rotation. The moment of inertia has relation with the mass and the radius of the bat as the following equation shows: I=∫R²dm. When the bat has a mass that is small and distributed close to a rotational axis of the bat, the bat would have a smaller moment of inertia. That is, the bat could be more easily swung and controlled. On the contrary, when the bat is heavy and has a large moment of inertia, it produces a relatively large momentum (momentum=mass×velocity) but could not be easily swung to create a high swing velocity. According to a study conducted by Fleisig at al in 2002, the linear and angular swing velocities of a baseball bat are significantly related to the moment of inertia, but not to the mass of the bat. Therefore, from the viewpoint of biodynamics, to obtain a fast swing velocity, the bat must have a reduced moment of inertia (Bailey, 1987). Thus, the study of Fleisig et al in 2002 suggests coaches and players to pay attention to the moment of inertia of the bat in addition to the mass thereof.

[0016] The bat having a higher mass usually has a thicker and longer barrel portion, and accordingly, a larger hitting area. However, the higher mass also results in slower swing velocity (Adair, 1990). Though it is possible to obtain a faster swing velocity by reducing the mass of the bat, the reduced mass and moment of inertia of the bat would decrease the effective mass of the bat, preventing the batter from easily and accurately hitting the ball within the sweet spot. Recently, there are manufacturers putting additional weight at the distal end of the bat, so that the effective hitting point on the bat is moved toward the distal end of the bat to somewhat enlarge the effective hitting section. However, this change would cause an increased moment of inertia of the batter's hands to adversely affect the swing velocity and the batter's ability in controlling the bat. In a study conducted by Noble & Eck in 1986, it was found that, by properly adding some weights inside a proximal end and the handle portion of the bat, it is possible to shift the effective hitting point toward the distal end of the bat, so that the effective hitting point has size and location capable of maximizing the benefit of the bat and minimizing a resistance during swing bat without the need of increasing the moment of inertia at a center of swinging. Thus, when the mass of the bat is distributed close to the impact point, such as in the case of a golf club, the bat would have a reduced rotational energy and relatively increased linear energy for the ball to fly farther (Adair, 1990). It can be known from the above analyses, swing velocity is the most important factor that has influence on the batter's hitting performance, while the mass and the moment of inertia of the bat also have different influences on the swing velocity. To meet the two major requirements of the bat to enable improved player's performance and reduced sport-caused injuries at the same time, it is desirable to employ the biodynamic principle to develop a bat having a dynamic moment of inertia (DMOI). A design concept of dynamic moment of inertia is characterized in that the swing velocity could be increased through reducing the moment of inertia of the bat at the initial stage of swing bat without the need of decreasing the bat weight, and that the requirement of increased impact energy could be met through the distribution of mass close to the impact point on the bat (Adair, 1990). It is also desirable to develop an improved bat having increased effective impact energy for the ball to fly faster and farther, and having good cushion effect to protect the batter's hands from injury.

[0017] U.S. Pat. No. 6,254,502 granted to Becker discloses a weighting system for sports balls and hitting implements. In the system, a hollow tube is embedded in the hitting implements, and two opposite shock absorbers and related locating plugs are provided at a hitting section near a front end of the hitting implements, and a weighting device is positioned between the two opposite shock absorbers. This design largely complicates the whole hitting implements and makes the bat just like a weighting bat at the initial stage of swinging the bat. That is, the bat has an increased resistance when it is swung, as compared with a normal bat, to adversely affect the swing velocity thereof, and accordingly requires improvement.

SUMMARY OF THE INVENTION

[0018] A primary object of the present invention is to provide a swing-and-hit device for ball games that is provided in an internal space near a handle portion thereof with a substance that moves in the swing-and-hit device when the latter is swung, and is therefore a substance having the property of dynamic moment of inertia. In a preferred embodiment of the present invention, the substance includes a plurality of tiny weighting granules, which are located at the handle portion when the swing-and-hit device for ball games is normally raised before being swung to hit, and move to an impact point on the swing-and-hit device due to the moment of inertia when the swing-and-hit device is forcefully swung.

[0019] With these arrangements, the swing-and-hit device for ball games according to the present invention has the moment of inertia to enable faster swing velocity and reduced muscle-exerted strength. Since the mass of the swing-and-hit device concentrates on the impact point at the instant of impact, the swing-and-hit device is able to generate increased impact energy. Moreover, since the tiny weighting granules absorb the vibration of bat produced during impact, possible sport-caused injuries to the user could be avoided.

[0020] In a preferred embodiment of the present invention, the tiny weighting granules are metal granules.

[0021] In another practicable embodiment of the present invention, the swing-and-hit device for ball games is internally provided with an elongate hole for holding the tiny weighting granules therein. The elongate hole has a distal end located at the best impact point, that is, the sweet spot, on the swing-and-hit device, so that the tiny weighting granules could freely move toward the impact point when the swing-and-hit device is swung.

[0022] The present invention is particularly suitable for applying to sports goods made of metal or composite material, because the tiny weighting granules may be sealed in the sports goods after they are molded or formed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

[0024]FIG. 1 is a sectional view of a swing-and-hit device for ball games in the form of a baseball bat according to a preferred embodiment of the present invention;

[0025]FIG. 2 is a graph showing sweet-spot-based swing velocity curves, wherein the upper curve is obtained from a baseball bat according to the present invention, and the lower curve is obtained from a general baseball bat;

[0026]FIG. 3 is a graph showing mass-center-based swing velocity curves, wherein the upper curve is obtained from a baseball bat according to the present invention, and the lower curve is obtained from a general baseball bat;

[0027]FIG. 4 shows two electromyograms (EMG) measured at a batter's musculus triceps brachii of left hands in swinging bat, wherein the upper curve is obtained from swinging a general bat, and the lower curve is obtained from swinging a bat according to the present invention;

[0028]FIG. 5 is a graph showing curves of vibration of a general bat, wherein the upper curve shows the vibration in a direction normal to the swing direction, the middle curve shows the vibration in a direction parallel to the swing direction, and the lower curve shows the vibration in a direction of the longitudinal axis of the bat;

[0029]FIG. 6 is a graph showing curves of vibration of a bat loaded with small-size granules according to the present invention, wherein the upper curve shows the vibration in a direction normal to the swing direction, the middle curve shows the vibration in a direction parallel to the swing direction, and the lower curve shows the vibration in a direction of the longitudinal axis of the bat; and

[0030]FIG. 7 is a graph showing curves of vibration of a bat loaded with large-size granules according to the present invention, wherein the upper curve shows the vibration in a direction normal to the swing direction, the middle curve shows the vibration in a direction parallel to the swing direction, and the lower curve shows the vibration in a direction of the longitudinal axis of the bat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Please refer to FIG. 1 that is a sectional view of a swing-and-hit device for ball games according to a preferred embodiment of the present invention in the form of a bat 10 used in baseball. It is understood, however, the principles and technical means of the present invention may also be applied to swing-and-hit device for other types of ball games, such as a golf club, a tennis rocket, etc.

[0032] As shown in FIG. 1, the bat 10 has a plurality of tiny weighting granules 12 pre-loaded therein. In practicable embodiments of the present invention, the tiny weighting granules 12 may be metal granules of different grain diameters. However, the weighting granules 12 may also be replaced with other substance that has the property of dynamic moment of inertia.

[0033] When the bat 10 is highly held in a normal manner, that is, in a position before being swung to hit a ball, the tiny weighting granules 12 are located in the bat closed to a handle portion 14 thereof. When the bat 10 is swung to hit a ball, the tiny weighting granules 12 displace in the bat due to a moment of inertia. In the illustrated preferred embodiment, the tiny weighting granules 12 are disposed in an elongate hole 16 formed inside the bat 10. A length of the elongate hole 16 may be calculated and specified in advance.

[0034] In the above-described swing-and-hit device for ball games according to the present invention, the tiny weighting granules 12 are located close to the handle 14 before the swing-and-hit device is swung to hit a ball, and are moved toward an impact point on the swing-and-hit device when the device is swung to hit a ball. More specifically, the tiny weighting granules 12 are moved to the sweet spot on the swing-and-hit device at the instant of impacting the ball. The swing-and-hit device for ball games according to the present invention with the above-described structure has at least the following advantages:

[0035] 1. At an initial stage of swinging, the swing-and-hit device has a mass distribution close to the handle portion thereof, and therefore has a lower moment of inertia to enable a faster swing velocity.

[0036] 2. At the instant of impact, the mass of the swing-and-hit device is concentrated on the impact point to generate higher effective impact energy.

[0037] 3. After the impact, the tiny weighting granules absorb the vibration of bat produced as a result of the impact to protect the user from possible sport-caused injury.

[0038] Though a baseball bat 10 is illustrated as an embodiment in FIG. 1, the present invention may also be applied to other types of ball games, such as rackets for badminton, table tennis, and tennis, and golf clubs. Taking the golf club as an example, the above-mentioned advantages of the swing-and-hit device for ball games according to the present invention also present when the golf club is raised and immediately swung downward to hit a golf ball. Since the golf club is usually a molded hollow member, it is particularly suitable for loading such freely movable weighting substance therein.

[0039] Alternatively, the substance having dynamic moment of inertia for loading in the above swing-and-hit device for ball games may be a type of liquid.

[0040] To enable adjustment of the amount of the weighting substance, such as the tiny metal granules, in the swing-and-hit device for ball games and thereby obtain a suitable ratio of the weighting substance to the swing-and-hit device by weight, an adjusting element, such as a screw cap, may be mounted near an end of the swing-and-hit device.

[0041] Experiment Results:

[0042] To prove the advantages of positioning a plurality of tiny weighting granules in the swing-and-hit device for ball games according to the present invention, including increased swing velocity, reduced strength to be exerted by muscles, increased effective impact energy, and enhanced cushion effect avoiding possible occurrence of sport-caused injury, the following experiment is conducted: a high-speed camera capable of taking 1000 frames per second is used to record a batter's swing movements from a position about seven meters immediately above the batter; and a movement analysis system is employed to analyze differences in swing velocity between the bat according to the present invention and a general bat. Experiment results are shown in FIGS. 2 and 3 and indicate that the batter swinging the bat of the present invention achieves swing velocities, separately measured at the sweet spot and the center of mass (COM), faster than that achieved with the general bat. And, the batter takes 176 milliseconds (ms) to swing the bat of the present invention, and 196 ms to swing the general bat. This shows the bat of the present invention enables faster swing velocity and shorter swing time. Therefore, the batter using the bat of the present invention has more time to judge the pitcher's ball course, and accordingly higher rate of accurate hitting as well as higher rates of safe hit and home run. It is proven from these data the bat having dynamic moment of inertia as provided according to the present invention indeed enables faster swing velocity, as compared with the general bat.

[0043] With respect to the reduction of muscle-exerted strength in swinging bat, a signal retrieval system supplied by Biopac Company, surface electrodes, an electromyographic pre-amplifier, an advanced signal converter, a MP100 interface card, and many other related goods are employed to collect the batter's electromyographic activities (signals). The collected signals are then filtered and recruited with Acqknowledge analysis software, version 3.5.7. According to past studies in related fields, the strength for swinging bat mainly comes from the musculus triceps brachii of left forearm, in the case of a right-handed batter (Kitzman, 1964; Marshall, 1979). Therefore, in the experiment conducted for the present invention, electromyographic activities of the batter's musculus triceps brachii of left arm are collected, and integrated electromyographic (IEMG) value and electromyographic peak value are adopted as two parameters to determine which type of bat is more effortless for use. The study results indicate the tested batter's IEMG value and electromyographic peak value are 0.0113 and 0.2982 millivolt (mv), respectively, during swinging a general bat, as shown in the upper curve in FIG. 4; and 0.0096 and 0.1768 mv, respectively, during swinging the bat of the present invention, as shown in the lower curve in FIG. 4. It is proven from these data the bat having dynamic moment of inertia as provided according to the present invention is indeed more effortless for swinging, as compared with the general bat.

[0044] In verifying the increased effective impact energy and the cushion effect of the present invention, the signal retrieval system supplied by Biopac Company, a three-dimensional accelerometer, the advanced signal converter, the MP100 interface card, etc. are employed to collect impact vibration signals of the bat of the present invention. The collected signals are recruited with Acqknowledge analysis software, version 3.5.7. According to past studies in related fields, metal granules of different volumes show different energy-absorbing ability. Therefore, in the studies conducted for the present invention, a general bat, a bat of the present invention internally loaded with small-size granules, and a bat of the present invention internally loaded with large-size granules are tested. The three-dimensional accelerometer is attached to each bat at a position 20 cm away from a rear end of the bat. The test results obtained from the general bat, the bat of the present invention with small-size granules, and the bat of the present invention with large-size granules are shown in FIGS. 5, 6, and 7, respectively. Wherein, the middle curves in the three figures indicate peak values of vibration in the swinging direction (that is, ball flying direction) at the instant the swung bats hit the ball. These peak values of vibration are 57.54 (G), 60.36 (G), and 69.08 (G) for the general bat, the bat of the present invention with small-size granules, and the bat of the present invention with large-size granules, respectively. It is found in the two bats of the present invention that there are two significant wave peaks appeared in the curves for them, and the peak value of the second wave peak is larger than that of the first wave peak. However, this condition does not appear in the curve for the general bat. This indicates the granules in the bats of the present invention create a double impact effect in the bats. In other words, the granules in the bat have forward momentum during the process of moving to generate additional energy. That is why the impact energy transferred to the ball from the bat of the present invention is larger than that from the general bat. Thus, it can be clearly seen the bat of the present invention using granules as it dynamic moment of inertia generates increased impact energy to hit the ball faster and farther.

[0045] The cushion effect of the present invention may also be verified from FIGS. 5, 6, and 7. The middle curves and the upper curves in FIGS. 5, 6, and 7 respectively represent the vibrations of the general bat, the bat of the present invention with small-size granules, and the bat of the present invention with large-size granules in the directions parallel to and normal to the direction of swinging bat, respectively. It is found the integrated vibration values and the vibration durations of the general bat shown on the curves are larger and longer than that of the bats of the present invention. The results are further shown in Table 2 as below. From these data, it can be seen that the bat of the present invention absorbs more impact energy than the general bat does, and absorbs the impact energy at a speed faster than the general bat. As a result, the bat of the present invention effectively reduces the possible injury at the batter's wrists and elbows caused by the vibration of the bat. In brief, the bat of the present invention provides better cushion effect than the general bat. TABLE 2 Vibration of Bat After Impact Small Large Type of Bat General Granules Granules Integrated value 0.5773 0.3944 0.3653 In Horizontal Direction (g × ms) Duration in 34 22 31 Horizontal Direction (ms) Integrated value 0.4907 0.2638 0.3963 In Vertical Direction (g × ms) Duration in 58 21 37 Vertical Direction (ms)

[0046] The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment can be carried out without departing from the scope and the spirit of the invention as defined by the appended claims. 

What is claimed is:
 1. A swing-and-hit device for ball games comprising a handle portion at where a user grips to swing said swing-and-hit device, a barrel portion having a predetermined length for hitting a ball or the like when the user swings said swing-and-hit device, and a substance having a property of dynamic moment of inertia being disposed in said swing-and-hit device close to said handle portion; whereby said substance is located close to said handle portion when said swing-and-hit device is normally raised before being swung to hit a ball or the like, and moves toward an impact spot on said barrel portion due to said dynamic moment of inertia when said swing-and-hit device is swung to hit the ball or the like.
 2. The swing-and-hit device for ball games as claimed in claim 1, wherein said substance having said property of dynamic moment of inertia comprises a plurality of tiny weighting granules.
 3. The swing-and-hit device for ball games as claimed in claim 2, wherein said tiny weighting granules are metal granules having specified grain diameters.
 4. The swing-and-hit device for ball games as claimed in claim 1, wherein said substance having said property of dynamic moment of inertia comprises a liquid.
 5. The swing-and-hit device for ball games as claimed in claim 1, wherein said swing-and-hit device is internally provided with an elongate hole having a predetermined length for holding said substance having said property of dynamic moment of inertia therein.
 6. The swing-and-hit device for ball games as claimed in claim 2, wherein said swing-and-hit device is internally provided with an elongate hole having a predetermined length for holding said substance having said property of dynamic moment of inertia therein.
 7. The swing-and-hit device for ball games as claimed in claim 3, wherein said swing-and-hit device is internally provided with an elongate hole having a predetermined length for holding said substance having said property of dynamic moment of inertia therein.
 8. The swing-and-hit device for ball games as claimed in claim 5, wherein said elongate hole has a distal end located within a best impact spot (sweet spot) on said barrel portion of said swing-and-hit device.
 9. The swing-and-hit device for ball games as claimed in claim 6, wherein said elongate hole has a distal end located within a best impact spot (sweet spot) on said barrel portion of said swing-and-hit device.
 10. The swing-and-hit device for ball games as claimed in claim 7, wherein said elongate hole has a distal end located within a best impact spot (sweet spot) on said barrel portion of said swing-and-hit device.
 11. The swing-and-hit device for ball games as claimed in claim 1, wherein said swing-and-hit device is molded from a metal material to seal said substance having said property of dynamic moment of inertia therein.
 12. The swing-and-hit device for ball games as claimed in claim 1, wherein said swing-and-hit device is molded from a composite material and is internally filled with said substance having said property of dynamic moment of inertia.
 13. The swing-and-hit device for ball games as claimed in claim 1, wherein said swing-and-hit device is provided near an end with a screw cap to enable adjustment of amount and weight of said substance in said swing-and-hit device via said screw cap. 